It is known to impart visual surface changes to pile fabrics containing thermoplastic pile yarns by directing pressurized heated fluid streams, such as air or steam, into selected areas of the pile surface of the fabric to thermally modify and change the visual appearance of the pile yarns in such areas. U.S. Pat. No. 3,613,186 discloses apparatus for producing pattern effects in pile fabrics by directing heated pressurized air into the fabric from a row of jets mounted in a long heater block which may be moved into two directions over the fabric which also may be moving. Air is supplied to the heater jets through individual air supply lines from an elongate air manifold, and a manually operated valve is provided in each supply line to permit certain of the jets to be cut off, or the air flow thereto to be altered, to change the particular design to be applied to the fabric. Heated air streams striking the pile fabric surface are stated to produce sculptured effects in the thermosplastic surface components thereof, and the pattern is produced by movement of the jets and/or fabric in directions related to each other.
Other apparatus for applying heated pressurized fluid streams to the surface of pile fabrics to alter their surface appearance are disclosed in U.S. Pat. Nos. 2,241,,222; 3,010,179; and 3,585,098. Generally such prior art apparatus provide a continuous flow of the heated fluid streams into the moving fabric during the patterning operation, and the pattern is obtained by relative movement of the fabric and stream applicator manifold during the treating operation.
In hot fluid stream patterning of pile fabrics and other substrate materials having thermally modifiable surface components, highly precise control of the pressure, temperature and direction of the streams striking the substrate material is required to obtain corresponding uniformity and preciseness in the resultant surface pattern formed in the material. If the heated fluid streams are discharged from a row of discharge outlets disposed across a moving pile fabric, unless the temperature and pressure of all streams across the width of the fabric is controllable, variations can occur in the shrinkage and compaction of the pile yarns contacted thereby, resulting in undesirable pattern irregularities in the fabric product.
Difficulties are encountered in maintaining precise control of the pressure and temperature of individual heated fluid streams when their rate of flow is controlled by use of conventional valves located directly in the heated fluid stream supply lines. For example, if the streams are discharged through individual jets having individual manually adjustable valves and a common heater for heating the jets, as in prior U.S. Pat. No. 3,613,186, it can be appreciated that when the rate of air fluid flow through one of the jets is varied by its manual control valve, the temperature of the air stream striking the fabric may increase or decrease because of the change in air flow through the heater. In like manner, if certain jets are completely cut off, the temperature of the heater block will tend to increase in that area, causing an increase in the temperature of the streams from the adjacent jets.
Recently, apparatus has been developed for more precise and uniform control of temperature and pressure of pressurized heated fluid streams to enable more precise and intricate patterning of relatively moving substrate materials, such as textile pile fabrics. Such apparatus comprises an elongate pressurized heated air distribution manifold having a row of heated air discharge channels located in closely spaced relation across the path of the moving substrate material to discharge heated air streams in the material surface. Air is supplied to the manifold through a bank of individual heater units which are controlled to introduce the air into the manifold at a uniform temperature at uniformly spaced locations across its full width. Flow directing baffles provided within the manifold uniformly distribute the incoming air as it flows across the manifold to the discharge channels, and the air is thus discharged therefrom in streams of uniform temperature and pressure.
Flow of the heated air through the discharge channels of the above-described manifold is controlled by the use of pressurized cool air which is delivered by individual cool air supply lines into each channel to block the passage of heated air flow therethrough. Each cool air supply line is provided with an individual control valve, and the cool air control valves are selectively opened or closed in response to signal information from a pattern source, such as a computer program, to block or allow the flow of heated air streams to strike the woving fabric in selected areas and impart a pattern thereto. Depending upon the pattern control information, the surface pattern applied to the fabric can be selectively varied in both lengthwise and widthwise direction of the fabric movement.
In use of such improved apparatus to pattern pile fabrics containing thermoplastic pile yarns, the pressurized air streams which strike selected surface areas of the moving fabric uniformly longitudinally shrink and compact the pile yarns into the fabric in such areas to form precise grooves of uniform depth, with the length of the grooves and their spacing in the fabric being controlled by the pattern control information sent to the cool air valves to produce a precise surface pattern characterized by untreated high pile areas and uniformly thermally treated low pile height areas.